Unlike other bacterial pathogens which must overcome host iron restriction to establish a successful infection, Borrelia burgdorferi, the causative agent of Lyme disease, is able to bypass iron limitation within a host by minimizing or perhaps even eliminating the need for iron. They accomplish this by eliminating pathways that include important iron- containing proteins and substituting other trace metals in metalloproteins that are found in B. burgdorferi. As a result, they do not appear to regulate gene expression based upon intracellular levels of iron as is seen in other bacterial pathogens. Instead, B. burgdorferi appears to regulate gene expression by monitoring levels of other metals, such as manganese or zinc. To investigate the observed metal- dependent gene expression, the PI has identified and cloned a gene encoding a putative metal-dependent repressor protein (PerR) from B. burgdorferi and identified a target sequence using a mobility shift DNA- binding assay. This sequence is 91 bp upstream of the start codon of a putative 2 gene operon encoding a glutamate transporter (gltP) and a NADH peroxidase (npx), suggesting that PerR may be involved in regulating an oxidative stress response by B. burgdorferi. A PerR homolog identified from Bacillus subtilis mediates cellular responses to oxidative stress and metal starvation in that bacterium. To understand the role this regulatory protein plays in the survival response of B. burgdorferi and to identify other genes it regulated, the PI proposed to (1) characterize PerR and its putative target sequence using mobility shift DNA-binding, primer extension, DNase I footprinting, and methylation/uracil interference assays, (2) assess the role of PerR and Nox in the oxidative stress response in B. burgdorferi by examining the effects of O2-, peroxide, and metal starvation on the expression of Nox and (3) identify additional genes regulated by PerR.